The present invention relates to vehicle performance indicator systems and more particularly to multi-mode electronic indicator systems which provides a selective digital display of odometer, tachometer, speedometer readings, as well as other vehicle performance parameters.
Presently known speedometers and tachometers such as the type commonly found in parent automobiles and trucks, as well as other surface vehicles, are subject to frequent mechanical breakdown and the resultant large expense for repairs. Thus, the tachometers and speedometers which are mechanically driven habitually require frequent replacement of the drive cables due to breakage. This problem is particularly acute in buses and trucks where the cables extenf for a great length from the rear engine to the instrumental panel. In the case of trucks, sharp bends in the cable aggravates the cable breakage problem. Furthermore, the electrical as well as the mechanically-driven ones exhibit readings which are very frequently inaccurate due to the fact that both types depend for their operation on mechanical springs as in the mechanical pointer assembly in the electrical readout display. Such reading inaccuracies are virtually unavoidable in such conventional systems due to the fact that mechanical springs after being subjected to repeat operation inevitably lose some of their original tensile strength thus resulting in an inaccurate position of the indicator needle and hence an erroneous reading.
High resolution conventional readout displays, of necessity, must include large characters and numerals as well as many subdividing lines which results in an unduly large meter face and increases the panel area which is required to accommodate such enlarged instruments. Such increased demand for panel space presents a serious problem since the availability of such space is highly limited. If, in order to meet this problem, the characters and numerals for the readout instrument are confined to a limited area the indicated speed becomes difficult for the vehicle operator to read and, in effect, distracts the driver's attention from the road for an unduly long period of time thereby creating a safety hazard. Furthermore, in order to increase the visibility of the readout to the driver and to maintain alignment of the readout meters with the driver's eyes it is necessary to locate the readout meter substantially in line with the driver's vision as he is facing forward.
Presently known electrical odometers generally comprise electronic circuits such as oscillators which employ capacitors, resistors and transistors to establish their output frequency. However, in view of the degradation of such electronic components over long periods of time, the stability of the oscillator output frequency deteriorates over such prolonged periods of time. Since most fleet vehicles are scheduled for preventative maintenance service based on the readings of the vehicle odometers or total engine RPM meters, inaccurate registration of these instruments results in premature replacement of materials and unnecessary labor costs. If, on the other hand, the above-mentioned instruments register fewer total mileage or total engine RPM than has actually elapsed, the delayed maintenance resulting thereby very likely leads to costly malfunctions in the vehicle.
Presently known excess indicator systems require the manual adjustment of a sliding control in order to set the desired maximum speed limit which then exceeded will produce an alarm signal. Such manual adjustment by the driver requires his close attention and thus becomes impractical and hazardous when the driver is passing through varying speed zones, and additionally because of the difficulty of aligning the sliding control, the inaccuracy of the desired control setting is frequently considerable.
It is therefore an object of the present invention to provide a vehicle performance indicator system which eliminates the disadvantages and drawbacks of presently known vehicle odometers, tachometers and speedometer instruments.
It is a further object of the present invention to provide a vehicle performance indicator system in the form of a single instrument which selectively provides odometer, total elapsed engine RPM, tachometer and speedometer readings to the vehicle operator requiring a minimum of diversion of the operator's attention from the traffic conditions.
It is yet another object of the present invention to provide a vehicle performance indicator system which because of its multiple instrument function, eliminates multiple stocking problems for vehicle fleet and vehicle manufacturing operations.